package com.youngjun.common.util;

import java.util.logging.Logger;

/**
 * @author https://github.com/twitter/snowflake/blob/snowflake-2010/src/main/scala/com/twitter/service/snowflake/IdWorker.scala
 * @author https://segmentfault.com/a/1190000011282426
 */
public class IdWorker {

    private static final Logger logger = Logger.getLogger(IdWorker.class.getName());

    private long workerId;
    private long dataCenterId;
    private long sequence;
    private long twepoch = 1288834974657L;
    private long workerIdBits = 5L;
    private long datacenterIdBits = 5L;
    private long maxWorkerId = -1L ^ (-1L << workerIdBits);
    private long maxDatacenterId = -1L ^ (-1L << datacenterIdBits);
    private long sequenceBits = 12L;
    private long workerIdShift = sequenceBits;
    private long datacenterIdShift = sequenceBits + workerIdBits;
    private long timestampLeftShift = sequenceBits + workerIdBits + datacenterIdBits;
    private long sequenceMask = -1L ^ (-1L << sequenceBits);
    private long lastTimestamp = -1L;

    public IdWorker(long workerId, long dataCenterId, long sequence) {
        // sanity check for workerId
        if (workerId > maxWorkerId || workerId < 0) {
            throw new IllegalArgumentException(String.format("worker Id can't be greater than %d or less than 0", maxWorkerId));
        }
        if (dataCenterId > maxDatacenterId || dataCenterId < 0) {
            throw new IllegalArgumentException(String.format("datacenter Id can't be greater than %d or less than 0", maxDatacenterId));
        }
        logger.info("worker starting. timestamp left shift "+ timestampLeftShift +", datacenter id bits "+ datacenterIdBits
                        +", worker id bits "+ workerIdBits +", sequence bits "+ sequenceBits +", workerid "+ workerId);

        this.workerId = workerId;
        this.dataCenterId = dataCenterId;
        this.sequence = sequence;
    }

    public long getWorkerId() {
        return workerId;
    }

    public long getDataCenterId() {
        return dataCenterId;
    }

    public long getTimestamp() {
        return System.currentTimeMillis();
    }

    public synchronized long nextId() {
        long timestamp = timeGen();

        if (timestamp < lastTimestamp) {
            System.err.printf("clock is moving backwards.  Rejecting requests until %d.", lastTimestamp);
            throw new RuntimeException(String.format("Clock moved backwards.  Refusing to generate id for %d milliseconds",
                    lastTimestamp - timestamp));
        }

        if (lastTimestamp == timestamp) {
            sequence = (sequence + 1) & sequenceMask;
            if (sequence == 0) {
                timestamp = tilNextMillis(lastTimestamp);
            }
        } else {
            sequence = 0;
        }

        lastTimestamp = timestamp;
        return ((timestamp - twepoch) << timestampLeftShift) |
                (dataCenterId << datacenterIdShift) |
                (workerId << workerIdShift) |
                sequence;
    }

    private long tilNextMillis(long lastTimestamp) {
        long timestamp = timeGen();
        while (timestamp <= lastTimestamp) {
            timestamp = timeGen();
        }
        return timestamp;
    }

    private long timeGen() {
        return System.currentTimeMillis();
    }


    public static long getWorkerIdByIP(String ipaddress) {
        int bits = 24;
        int shift = 64 - bits;
        long ip = IPUtils.ipV4ToLong(ipaddress);
        return (ip << shift) >>> shift;
    }

}